Multi-element antenna arrays can provide performance advantages over single element antenna arrays. For example, radiation from multiple elements can be phased so that energy constructively adds in desired directions and destructively cancels in undesired directions. Multiple elements can also allow for gain increases. When adjustable phase shifts and gains are provided to the individual elements, adaptation of the antenna array can be performed in real time, enabling additional performance gains.
Unfortunately, multi-element antenna arrays can tend toward the complex and expensive. For example, for an aircraft platform, antenna elements may be required on both the top and bottom of the aircraft to enable communications in all desired directions (e.g., to satellites in orbit and to fixed stations on the ground). A large number of individual elements may be required to provide desired coverage directions and aperture size. As antenna arrays increase in size there is attendant increase in cost, power, and size due to power amplifiers, low noise amplifiers, phase shifters, and similar components associated with each individual element. Moreover, switching and feed systems become more complex as the number of elements increases. Accordingly, very large arrays, while desirable from a theoretical radio communications performance standpoint, have generally proven to be of limited feasibility except in specialized applications.